Question

我有一个示例套接字程序。客户端只发送数字，服务器回送它们。

客户端：

public class Client {
private Socket socket;
private BufferedReader in;
private PrintWriter out;

public Client(String hostname, int port) throws IOException {
    socket = new Socket(hostname, port);

    //Create a BufferedReader with buffer size of 1
    in = new BufferedReader(new InputStreamReader(socket.getInputStream()), 1);
    out = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()));
}

public void sendRequest(String x) throws IOException {
    out.print(x + "\n");
    out.flush(); 
}

public void close() throws IOException {
    in.close();
    out.close();
    socket.close();
}

public String getReply() throws IOException {
    String reply = in.readLine();
    return reply;
}

public static void main(String[] args) {
    try {
        Client client = new Client("localhost", 4949);

        for (int i = 0; i < 100000; i++){
            System.err.println("Sending: "+i);
            client.sendRequest(String.valueOf(i));
        }

        for (int i = 0; i < 100000; i++){
            client.getReply();
        }

        client.close();
    } catch (IOException ioe) {
        ioe.printStackTrace();
    }
}
}

服务器：

public class Server {
private ServerSocket serverSocket;

public Server(int port) throws IOException {
    serverSocket = new ServerSocket(port);
}

private void handle(Socket socket) throws IOException {
    System.err.println("client connected");

    BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

    // Create a PrintWriter with buffer size 1
    PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()), 1));

    try {
        for (String line = in.readLine(); line != null; line = in.readLine()) {
            out.print(line + "\n");
            out.flush();
        }
    } finally {
        out.close();
        in.close();
    }
}

public void serve() throws IOException {
    while (true) {
        // block until a client connects
        Socket socket = serverSocket.accept();
        try {
            handle(socket);
        } catch (IOException ioe) {
            ioe.printStackTrace(); // but don't terminate serve()
        } finally {
            socket.close();
        }
    }
}

public static void main(String[] args) {
    try {
        Server server = new Server(4949);
        server.serve();
    } catch (IOException e) {
        e.printStackTrace();
    }
}
}

这似乎是一个显而易见的问题，但为什么客户端的输入缓冲区没有填满并导致死锁？客户端在阅读任何回复之前会发送10000个号码。这不会导致客户端的接收缓冲区填满，也会导致服务器的发送缓冲区填满吗？我甚至将BufferedReader和BufferedWriter的缓冲区大小尽可能小。但是，当我运行此代码时，没有死锁。

Answer 1

因为您忽略了发送方处的套接字发送缓冲区的存在，以及接收方处的套接字接收缓冲区。它们位于内核中，它们可以清楚地保存服务器之间的所有输出。

客户端 - 服务器套接字程序没有按预期遇到死锁

1 个答案: